TX-9500II Power Supply Issues

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PIONEERFREQ
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Turned on my TX-9500II the other day, lamps came on but no output.
Symptoms:
Unit is all original. Never been recapped.
No output with FM, AM, Rec Level Check regardless of any switch settings.
No meter movement.
No wide, narrow or stereo lights.

Checked the power supply voltages by checking pins of PA2002 on AWR-128:
1 = 26.4v ok
3 = 0.7v should be 3.4v
8 = 1.2v should be 4.2
10 = 0v should be 13v

Q1:
No shorts.
Collector = 26v ok
Base = 0v should be 13v
Emitter = 0v should be ?

AWR-128 pins 3,4,5 and 6 don't seem to be shorted to ground.

I intend to check C6, C8 and C12 then go from there. If they're ok, I'm thinkin' bad PA2002.

Feel free to chime in...
 
Agreed. I see a couple allegedly NOS on the bay but we'll see... I'll probably just replace the three caps in the area and retest. Hope to get some time tomorrow night.
 
Best to isolate the 13V supply from the loads to determine if there is a overload on the 13V line. If it is still wrong with no loads, check the ecaps as you say, then if the reg is dead I suggest to redesign the regulator, something as simple as a LM317T to replace the PA2002 should do the trick. let me know if you need more help, I have lots of LM317T, and you live close to me.
Looking at a pic of the AWR-128, it looks easy enough to remove the PA2002 and mount a LM317 in it place using an insulator to isolate the live tab from chassis ground.
 
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UGH, had to work overtime tonight. Maybe tomorrow...
I probably have a couple 7812s kicking around and thought about using one of those. Just need an hour or so to troubleshoot a little more
 
Sure you can use a 7812, you can lift its o/p up to what is required with a couple of diodes in the ground lead or a feedback arrangement as shown in the datasheet.
 
Looks like the PA2002 for sure.
Replaced all the electrolytics on AWR-128 (was planning on doing this at some point anyway).
No change.
Disconnected wires from pins 3, 4, 5 and 6 on AWR-128.
No change.
Just for fun, I tested Q1 out of circuit. Diode test looks fine.
Also just for fun, checked PA2002 voltages with Q1 removed.
No improvement.

So now I have to decide: keep it as original as possible and buy a replacement PA2002 or do a mod with a modern component.
 
Made the decision to proceed with a mod but in such a way that it could easily be removed and reverted back to original.

I didn't have any 7812s in stock so I had to go with a 7808. Most 78xx datasheets show how to raise the output voltage of a fixed voltage regulator like the one found here on Mouser's web site on page 19:
http://www.mouser.com/ds/2/149/LM7805-189995.pdf

Here is what I followed:
index.php


R1 = 1k
R2 = Needs to be just the right value. In my case I needed about 410 ohms so I used 2 resistors in parallel: 470 ohms and 10k ohms
This gave me an output voltage of 13.08 volts. Good enough.

Wired everything up on an old piece of project board I had. I chose to mount the 7808 on the back side of the board so that the board could be held in place with the tab screw and for space reasons. I desoldered the PA2002 and mounted the mod board on the tab that the PA2002 was mounted on making sure to isolate the 7808 tab with a collared washer and a silicone pad. Normally this is not necessary but because we are raising the output voltage above the fixed value using the ground pin, this raises the voltage of the tab above zero.

index.php


I just ran wires from the mod board to the existing PA2002 holes:
Input: pin 1
Ground: pin 5
Output: pin 10

Powered it up with the wires from pins 3, 4, 5 and 6 on AWR-128 disconnected. Voltages all looked good so I reconnected all of the wires. Powered it on and we have the dancing banana. Hooked it back up to the main system and let it run for 2 hrs with no issues.

It's not the prettiest work I've done but it's ok for scrounged parts.

index.php
 

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Logical choice, well done,
Hope you have a good antenna setup for that 9500. Try this test, tune to 92.3MHz, point antenna to NE (Georgina Island) and see if you can get NISH (CFGI), would probably need some high ground for best reception. In know Pickering College also uses 92.3MHz for non-commercial use. NISH is all I listen too, no commercials and all rock, blues.
My other test, is St. Catharines 91.7 Giant FM(CIXL)
I just got my Crown FM1 going again, finally found the controller IC from littlediode.com, almost as nice as a 9500, I do like the digital tuning and fav station memory even if it is only 5 of them.
Lets hope the other PA ics hold up in your 9500.
 
Logical choice, well done,
Hope you have a good antenna setup for that 9500. Try this test, tune to 92.3MHz, point antenna to NE (Georgina Island) and see if you can get NISH (CFGI), would probably need some high ground for best reception. In know Pickering College also uses 92.3MHz for non-commercial use. NISH is all I listen too, no commercials and all rock, blues.
My other test, is St. Catharines 91.7 Giant FM(CIXL)
I just got my Crown FM1 going again, finally found the controller IC from littlediode.com, almost as nice as a 9500, I do like the digital tuning and fav station memory even if it is only 5 of them.
Lets hope the other PA ics hold up in your 9500.

Thanks. All I have at present is a pair of rabbit ears in the attic that I'm unable to adjust (without climbing up there via one of the closets). Mostly listen to Jazz FM or CIUT.

It's a great tuner but you're right, there are components that could fail that would be difficult to find. I also haven't recapped this unit as I don't have equipment or the experience to align it. At least the power supply is now recapped.

This is the third failure in my stack in the last five years: PA 2002 in the TX-9500II, zener diode in my PL-560 power supply and a transistor in the protection circuit in my SPEC 4. That has not made me want to give up on it though.
 
I think the tuner deserves more than rabbit ears :) CIUT is not very powerful, must have hissy stereo, signal around 2-3?

I do not see any ecap's that would affect the alignment of this tuner. the mpx pcb looks easy enough to do.
You are not doing too bad for failures considering the age of the stuff.
If you mess up I am local, I have test equipment to align/fix this beast, but I did read on fmtunerinfo it ain't easy to align.
Our panelist Bob adds, "I dragged out the TX-9500II and gave it a total alignment. Wow, it was not easy. There were a million adjustments and almost more cans than the Charlie (and I could *touch* these!). I was amazed when finished."
 
Yeah, it does deserve a better antenna (CIUT is almost a 3 on the signal level meter). It's on my list but there always seems to be higher priorities. I do most of my electronic stuff in the winter when some of my other activities start to wane but I was missing my tuner so I pulled it and just had to work on it in smaller time slices than I typically like. Maybe in another few weeks I'll pull it back out of the rack and do the recap.

I read that article too. That is one of the things that made me hesitate going ahead with the recap. Thanks for the offer of assistance. Hopefully it won't come to that LOL. What's your general location? I'm close to the hospital.
 
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